In the area of loaders, such as loading vehicles or telescopic loaders and the like, systems are previously disclosed which protect the vehicle from getting into an unsafe load condition. Unsafe load conditions arise, for example, when the vehicle overturns over the front axle as the result of a forward shift in the center of mass. In these systems, the hydraulic functions are braked and are brought to a halt as soon as a sensor detects that the vehicle is threatening to tip. Once the hydraulic actuators have been stopped, the only functions that can still be operated are those which bring the vehicle back into a safe condition, for example raising the extension arm, tilting back the implement or the load and retracting the extension arm.
In systems of this kind, it is sensible not to arrest the movements of an extension arm too abruptly, as this can lead to overturning of the vehicle due to the inertia of the load and the extension arm. It is sensible to slow down the functions progressively the closer the vehicle approaches to a critical operating condition or load condition.
WO 2004/007339 A1 discloses a system of this kind. Here a tipping moment acting on the vehicle is detected by a sensor and is transmitted to an electronic control unit. Also provided are a number of hydraulic cylinders for the lifting, lowering and telescoping of a telescopic extension arm as well as the electro-hydraulic actuation of the hydraulic cylinders. The system provides for the hydraulic functions for operating the hydraulic cylinders to be slowed down as a set threshold value for the tipping moment is approached, before the hydraulic cylinders come to a complete standstill. In this case, for example, the load signal is processed electronically and the possibilities for operation by the user are reduced and/or operation is prevented. The more advanced the technology, for example by the use of electronic control units, the easier is the intervention by means of the electronics.
For hydro-mechanical systems with mechanically controlled control devices, the characterizing features disclosed in WO 2004/007339 A1 do not find an application, because a hydraulically pilot-controlled system intervention is not possible in a controlled manner by such simple means in the functions, due to the absence of suitable electronics.